People can go onto websites to find out how much a website is worth, these websites will show how much money you could make by things such as google adsense and such. This doesn't mean you are making this money at the very moment, this is a simple estimation that a machine is calculating as a possibility, not a guarantee. So when people say this sort of thing to you, it usually isn't true and should just be ignored.

Sorry if this ruins your mood in any way, I just want to share my knowledge with this sort of thing to you.

In addition to what Jadster has said, generally these sites all work off of one general estimate, meaning even if you did have google adsense on your forum or another advertising system then it might not make $300 or something similar. One a side note, if you ever did use google adsense or something similar you'd first need to disable the forumotion ads because Forumotion ads are already on your forum and you can't have two different ad hosts on one forum.